1. Field of the Invention
The present invention relates to an ink jet recording apparatus that discharges ink from the ink discharge unit of the recording head unit, which is arranged to face the recording surface of a recording medium, in accordance with recording data for recording by the adhesion of ink thereto, and discharges fixing liquid to fix ink simultaneously.
Also, the present invention relates to an ink jet recording apparatus, and more particularly, it relates to an ink jet recording apparatus that discharges to a recording medium a liquid containing the substance that insolubilizes or coagulates the pigment (which may be referred to as a colorant) in ink before or after the formation of dots recorded (or printed) on the recording medium by the adhesion of ink discharged from each recording head.
2. Related Background Art
For an ink jet recording apparatus, there has been proposed a method for preventing the quality of images from being lowered due to running of ink when images are recorded on the recording surface of a textile or paper recording medium in accordance with recording data. In the specification of Japanese Patent Application Laid-Open No. 58-128862, for example, it is disclosed that a fixing liquid is caused to adhere to the same positions as those in which pixels are formed in order to fix ink on the recording surface before such pixels are formed by the adhesion of ink droplets from the ink discharge unit of the recording head unit to such recording surface or after the pixels are formed by the adhesion of ink droplets from the ink discharge units to the recording surface.
Also, as disclosed in the specification of Japanese Patent Application Laid-Open No. 64-63185, for example, pixels are formed by the adhesion of ink droplets from the ink discharge unit of recording head unit to the recording surface after a chemical compound that insolubilizes dyestuff contained in ink is caused to adhere to the recording surface of a recording medium or as disclosed in the specification of Japanese Patent Application Laid-Open No. 5-202328, for example, a fixing liquid that fixes ink is caused to adhere to the recording surface by the application of ink jet method or by means of roller coating in order to make the surface waterproof before pixels are formed by the ink droplets on the recording surface. It has also been proposed that before ink and its fixing liquid reach a recording surface, that is, at the time when the ink droplets and fixing liquid fly from the respective recording heads, the ink droplets and fixing liquid are mixed, and such mixture is caused to adhere to the recording surface so that waterproof images are formed on it.
As described above, since the fixing liquid adheres to the entire recording surface of a recording medium, there is a possibility that the fixing liquid is wastefully consumed, because it adheres to the portions other than those pixels that require the application of the fixing liquid. Also, when images are formed by use of ink of plural colors, there are some cases where a color mixture takes place due to the fixing liquid that has been applied more than necessary.
Also, in accordance with the conventional examples described above, processing liquid is applied to all the positions of recording dots formed on a recording medium. Therefore, processing liquid is consumed more than necessary, and particularly when a color recording is executed by use of ink of many colors, a problem is encountered that color mixture occurs due to processing liquid used in an amount more than needed. In order to solve a problem of the kind, there has been proposed in Japanese Patent Application Laid-Open No. 8-52867 (hereinafter referred to as a related technical example) a technique that makes it possible to maximize the function of such processing liquid for the enhancement of the fixing and waterproofing capabilities of ink by its adhesion only to the optimal locations in an optimal quantity.
Here, in conjunction with the accompanying drawings, the description will be made of an example in which an image formation method adopted for the related technical example described above is applied to a color ink jet printer. FIG. 8 is a perspective view which schematically shows such color ink jet printer.
In FIG. 8, a reference numeral 111 designates a head unit provided with recording head 101, 102, 103 and 104, and a head 105 for use of processing liquid. These heads 101 to 105 are provided with 64 discharge ports each, for example, on the respective surfaces facing a recording sheet 307 serving as a recording medium in the conveying direction of the recording sheet 307. Also, for these head 101 to 105, ink paths or processing liquid paths are arranged to be conductively connected with the respective 64 discharge ports. Then, for the corresponding liquid paths, electrothermal transducing elements are formed on the substrates that constitute the heads, respectively, to generate thermal energy for discharging ink or processing liquid. The electrothermal transducing elements generate heat by means of electric pulses to be applied in accordance with recording data whereby to create film boiling in ink or processing liquid and discharge ink or processing liquid from the discharge ports with the development of air bubbles caused by the film boiling thus created. A common liquid chamber is arranged to be conductively connected with each of the liquid paths of the heads 101 to 105, respectively, and ink or processing liquid retained in each common liquid chamber is supplied to the respective liquid paths in accordance with each discharge operation in each of the liquid paths.
The head unit 111 is mounted on a carriage 302. The carriage 302 is slidably coupled with a pair of guide rails 303 extended in parallel with the recording surface 307A of a recording sheet 307. In this way, the head unit 111 travels along the guide rails 303. Along this traveling, the head unit performs recording by discharging ink or processing liquid by the timing that will be described later. After the traveling of the head 111, the recording sheet 307 is conveyed for a given amount in a direction indicated by an arrow. Then, the recording operation is resumed. With the repetition of such operation, recording is executed one after another on the recording sheet 307.
The recording sheet 307 is conveyed by the rotation of a pair of conveying rollers 304 and 305, each arranged above and below the recording surface 307A, respectively. Also, on the reverse side of the recording surface 307A of the recording sheet 307, a platen 306 is arranged to keep the flatness of the recording surface 307A.
In this respect, the traveling of the carriage 302 is possible by means of a belt (not shown) attached to the carriage when the belt is driven by a motor. Also, the conveying rollers 304 and 305 are made rotative likewise when the motor is driven and its rotation is transmitted to them.
FIG. 9 is a block diagram which shows the control system of the printer represented in FIG. 8. In FIG. 9, a CPU 100 executes control and data processes for the operation of each unit of the apparatus including the dot formation of processing liquid which will be described later. On a ROM 100A, procedures and others are stored for the execution of such processes. Also, a RAM 100B is used as a work area for the execution thereof.
In accordance with recording data, ink and processing liquid are discharged from the head unit 111 when the CPU 100 supplies to the head driver 301A the driving data and driving control signals (discharge timing) with respect to the electrothermal transducing elements. Further, the CPU 100 controls the carriage motor 200 to move the carriage 302 and a sheet feeding motor (PF) motor 500 to rotate the conveying rollers 304 and 305 through the motor drivers 200A and 500A.
FIG. 10 illustrates the head unit 111. A reference numeral 101 designates a recording head to discharge cyan (C) ink. Likewise, a reference numeral 102 designates a recording head to discharge magenta (M) ink; 103, a recording head for yellow (Y), and 104, a recording head for black (K). Also, a reference numeral 105 designates a head for use of processing liquid, which discharges the processing liquid that insolubilizes the dyestuff serving as a colorant in ink. The composition of ink and processing liquid will be described later. In this respect, for a printer used for a monochromatic color, the head 105 for use of processing liquid should be provided only for a recording head to discharge black ink, for example.
FIGS. 11A and 11B are views which illustrate the facing relationship between the head unit 111 and recording sheet 307. The head 111 performs its main scan in the direction indicated by an arrow A, while discharging ink of each color, and processing liquid from the head 105. Then, the recording sheet 307 is fed in the direction indicated by an arrow B (in the sub-scanning direction). In this way, images are recorded on the recording surface 307A of the recording sheet 307. In this example, the head 105 for use of processing liquid is positioned on the front side in the main scanning direction. It is arranged that ink of each color is discharged from the recording heads 101, 102, 103, and 104, respectively, after processing liquid has been discharged from the head 105. In other words, after dots of processing liquid are formed by the adhesion of the processing liquid to the recording surface 307A, ink of each color is discharged for the formation of recording dots to record images. In this respect, it may be possible to arrange a structure on the contrary so that after the formation of recording dots, the processing liquid is discharged to form dots of processing liquid.
Now, the description will be made of the discharge operation of ink and processing liquid.
Here, it is assumed that recording data are made as shown in FIG. 12. The data take OR with the corresponding recording data on each ink of C, M, Y, and K, and the entire discharge positions of ink that correspond to the data, that is, the positions of recording dots formed by each ink, are indicated by a mark .largecircle., respectively. This is designated as D1. The numerals 1 to 10 in FIG. 12 indicate the positions where dots are formed in the main scanning direction. Also, the reference marks a to h indicate the recording positions in the sheet feeding direction.
FIG. 13 is a view which illustrates a method for setting control regions at 311 to 330 in FIG. 13 with respect to the recording data shown in FIG. 12. In this case, each control region is a small area equivalent to 2 dots.times.2 dots. If data on the recording dot formation is present at a given position in each small area, a recording dot D1 is formed after a dot of processing liquid (designated by a mark D2) has been formed in such position on the recording surface 307A. In other words, a mask pattern of two dots by two dots is activated with respect to the recording data, thus producing the data for use of processing liquid. As to the region 311, for example, the data on recording dot formation is present at the coordinates (2, b) (lower right-hand in the region) in FIG. 13, and then, in the corresponding position in the control region 316 in FIG. 13, a .largecircle. is present. Then, processing liquid is discharged to the position at the coordinates (2, b) in the region 311 to form a dot D2 of processing liquid. In other words, according to this example, a structure is arranged so that processing liquid is discharged in an amount of approximately 25% of the OR with the recording data corresponding to each of C, M, Y, and K color ink for recording an image, and after that, the recording dots are discharged. By experiments, it has been confirmed that it should be good enough for processing liquid to be discharged approximately in this amount if the compositions of the processing liquid and ink are such as to be described later. In this case, the head 105 for use of processing liquid discharge is of the same structure as the other heads 101 to 104 for use of recording. The discharge amount of each nozzle is also the same.
In this respect, it may be possible to set the control regions arbitrarily corresponding to the discharge amount of the head that may be used for discharging processing liquid within a range where one dot D2 of processing liquid can produce its effect, not necessarily limited to the setting of a control region in an area equivalent to two dots by two dots.
Nevertheless, according to the related technical example described above, the positions where processing liquid dots are formed on a recording medium are set always the same. Therefore, for example, with the head 105 for use of processing dot formation, which is structured the same as those heads 101 to 105 for use of recording dot formation, the same nozzles of the head 105 are used for discharging processing liquid to form the dots thereof. As a result, the use of nozzles are biased. Also, if a differently structured head should be adopted in place of the head 105 for use of liquid dot formation, while and heads 101 to 104 are still used for forming recording dots, there is a need for the provision of a new head with an inevitable increase of costs. Even with such costly arrangement, only fixed formation of processing liquid dots is executable, making it difficult to flexibly deal with any special modes of processing liquid discharges.
Also, when a control is made to suppress the discharge amount of processing liquid to approximately 25% of each printing location of every C, M, Y, and K, it is inevitable that some one dot of four dots in a certain discharge location presents a complete dot on dot state if the discharge control of processing liquid is made in the same way as the discharge control of color ink. Then, color ink is fundamentally discharged to the three positions where no processing liquid has been discharged for the intended treatment. From the purpose for which processing liquid is discharged, it is desirable to apply the processing liquid to as many color ink discharge positions as possible. Here, however, processing liquid should be discharged to all the discharge positions of C, M, Y, and K if discharge signals are generated in the same process as for discharging color ink without any particular control. In other words, there is no alternative fundamentally but to discharge color ink to the positions where no processing liquid has been discharged unless processing liquid is discharged to cover recording locations 100%.